1. Field of the Invention
This invention relates to a running control device in cargo handling vehicles and, particularly, to a novel running control device in a cargo handling vehicle having one power plant for both rotating the driving wheels of the vehicle via a continuously variable transmission and driving a cargo handling hydraulic pump, which changes the speed ratio of the continuously variable transmission to control the running speed of the cargo handling vehicle.
2. Description of the Prior Art
Heretofore, some cargo handling vehicles equipped with a cargo handling device, such as a fork lift truck or a shovel loader, etc., had one engine, functioning as a power plant, for rotating the driving wheels via a continuously variable transmission and for driving a cargo handling hydraulic pump. In these types of cargo handling vehicles, the continuously variable transmission was of the torque converter type and the static hydraulic type.
In the case of the torque converter type vehicle, when it is desired to perform the cargo handling work while the vehicle is running at a low speed, an accelerator pedal must be stepped on to rev up the engine because the rate of revolution of the cargo handling hydraulic pump must be increased for that work. If so accelerated, the vehicle speed goes up as the revolution rate increases. To overcome such inconveniences, the vehicle speed was adjusted so as not to increase by depressing an inching pedal in the past. Accordingly, the cargo handling manipulation while the vehicle is running was troublesome and required a skill, and it was very difficult to perform the cargo handling work while compensating for a variation in vehicle speed caused by the cargo handling manipulation.
In the case of the cargo handling vehicle having the static hydraulic type continuously variable transmission, the vehicle speed was maintained constant by revving up the engine and, at the same time, by bringing down the speed ratio through manipulation of a swash plate manipulation pedal, or the vehicle speed was adjusted by means of the swash plate manipulation pedal while keeping the engine in the revved-up state irrespective of the conditions of running or cargo handling. However, even in this case, similarly to the above case, it was very difficult to perform the cargo handling work while compensating for a variation in vehicle speed caused by the cargo handling manipulation, and there was a problem relating to noise or fuel consumption because the engine was revved-up irrespective of either the running condition or cargo handling work.